1. Field of the Invention
This invention concerns a novel method for shell removal from hard boiled eggs. In particular, this invention concerns the removal of shell from the hard boiled eggs using chemical means or, in alternative, a combination of chemical with mechanical means. The method allows peeling of freshly laid eggs and results in peeled hard cooked eggs with extended duration shelf life and with preserved flavor, texture and appearance.
2. The Background and Related Disclosures
Eggs are an important nutritional product. Hard cooked, peeled and packaged eggs are becoming increasingly popular in the institutional food service, in the food industry and in retail marketing. However, the extent of the hard-cooked eggs usage depends primarily on successful overcoming of problems connected with their boiling, storing, preservation, shelf life, taste, peeling and a large scale processing.
While the numerous advantages connected with the use of the hard boiled eggs, such as providing a nutritious food, healthy source of protein, good taste, colorfulness, long shelf life, ease of preparation and low cost, among others, are evident, the industrial or large scale usage of the hard boiled eggs depends on how the problems connected with the use of hard boiled eggs can be prevented or overcome.
Primary problems connected with a large scale production of the hard boiled peeled eggs are their boiling and peeling. Both boiling and peeling, but particularly peeling, can seldom be done without a damage to the egg white albumen, without affecting the shape and texture of the hard boiled eggs, or without effecting their taste or appearance. Generally, current methods used for the large scale hard boiled eggs peeling result in a low yield due to the damage to high percentage of eggs.
The problems connected with the peeling of the hard boiled eggs are sufficiently evident by the number of developed devices, apparatuses and methods. Until now known and used methods for eggs boiling and peeling include many types of mechanical peelers or egg shelling devices such as the device described in the U.S. Pat. No. 4,787,306 utilizing the tap water pressure for peeling eggs by water jet; apparatus for continuous peeling of boiled eggs according to the U.S. Pat. No. 4,311,089; automatic machine for peeling hard-boiled eggs described in the U.S. Pat. No. 4,344,359; or a combination of vibration and washing procedures such as shell removal from partially frozen eggs by mechanical vibrator which cracks the shell and then washes it out with water jet, according to the U.S. Pat. No. 3,634,531. Other mechanical egg peeling methods and apparatuses are described in U.S. Pat. Nos. 4,686,895, 4,191,102, 4,082,856, 4,056,051, 3,951,055, 3,859,907 and others.
Most of the mechanical devices developed for peeling of shell and membrane from the hard cooked eggs utilize the eggs cooked in water to a hard boiled level, followed by immediate cooling in order to prevent gray discoloration of the yolk's surface. Then the egg shell is cracked and peeled by various types devices as described in above cited patents.
The wholly mechanical peeling, however, produces inconsistent results. For example, some eggs are peeled completely, without leaving behind the shell or membrane residue, but some eggs, peeled in the same manner, remain to have the shell or membrane residues attached to the albumen. Similarly, some eggs have broken or damaged albumen and some eggs do not. Consequently, following the mechanical peeling the eggs must be manually sorted to separate those having the broken albumen or having the shell or membrane residues adhering to the albumen. Since only the wholesome undamaged and wholly peeled eggs are acceptable for restaurants and catering, the manual sorting is necessary before the undamaged eggs are moved to the packaging line. The eggs which have broken albumen are sorted out and are only used for salads and such other uses where the appearance and undamaged albumen does not matter. The eggs which have remainders of the shell or membrane still attached after the mechanical peeling are either manually cleaned or chopped to egg salad, both causing economical loss, because normally, the eggs to be used for egg salad are processed by separation of white and yolk and each cooked separately and chopped later. Such process is much faster, cheaper and easier. Consequently, any use of hard boiled eggs after peeling for egg salad is costly and therefore uneconomical.
Generally, operating such egg-peeling equipment results in lower yield of wholesome peeled eggs and thus a greater loss as the various machines tend to damage a high percentage of the eggs by breaking and cracking the eggs white albumen. Since the high percentage of hard boiled eggs is used for catering which requires that the eggs not only taste good but also look good, the damaged albumen is not only undesirable but it is often not acceptable.
Moreover, as described above, when mechanical peeling devices are used, some of the shell residues tend to adhere to the egg white requiring a time consuming and costly manual sorting and cleaning. Moreover, the remnants of the shells may contribute to a spoilage and contamination of the eggs and result in shorter shelf life of the product. Another very serious disadvantage of the mechanical peeling is that newly laid eggs cannot be successfully peeled by currently available equipment. The reason for this is a long known fact that the physical characteristics of the egg, particularly egg white changes during aging. These changes may be readily observed. The cooked albumen in fresh eggs is soft and more fragile, in aged eggs, it is more firm and solid. The membrane of the freshly laid eggs is strongly attached to both the shell and the albumen. In the freshly laid eggs, the inner shell membrane adheres closely to the cooked or coagulated albumen because the egg content contains carbon dioxide and is thus relatively acid having pH around 7.5. As the egg ages, carbon dioxide escapes, the acidity level is reduced and the pH is raised up to 8.5-9.8, resulting in the improved peelability. Previous attempts to remove the shell from the newly laid eggs therefore often resulted in damaged albumen due to breaking of the membrane having attached pieces of albumen. Since the fresh eggs are difficult to peel without extremely high losses, it is necessary to either age the eggs by storing them in the cold refrigerated room for two to three weeks or to age these eggs artificially.
In terms of a storage, the availability of the cold storage for two to three weeks is needed in order to naturally elevate the pH of the egg's albumen to optimal pH 8.6, at which pH it is possible to separate the membrane from the albumen. Even then, consistency of the peeling is a problem and invariably some batches will peel and other will not. And, of course, at that time the eggs are already two weeks old.
There were some attempts made to speed up the aging of the eggs by artificially raising the pH of the albumen by acceleration of the loss of carbon dioxide. As described in U.S. Pat. No. 3,216,828, such aging method facilitates the shell removal from the hard boiled eggs. Artificial aging according to the invention described in '828 patent is achieved by the treatment of the eggs with chemicals which absorb carbon dioxide. An exposure to ammonia fumes for 15 minutes during which time the pH of the albumen was raised to above 9.1, resulted in the easier mechanical removal of the shell. However, such long exposure to strong fumes may effect the taste of the eggs as it may result in the introduction of undesirable ammonia odors into the egg meat which odors must be removed by aeration. Thus, this process necessitates an introduction of another step, i.e., aeration. Alternatively, the eggs may be aged by soda lime, a mixture of sodium and calcium hydroxides.
All the above methods create many problems and encompass many disadvantages. In particular, these methods or devices leave behind a shell residue, cause broken albumen, damage high percentage of hard boiled eggs, require manual sorting, affect the taste, appearance and texture of the eggs, and require an introduction of additional methods for sorting, washing, aeration, taste restoration and odor removal. Moreover, as the newly laid eggs cannot be peeled, two to three weeks storage and refrigeration is additionally needed to raise pH of the albumen which allows its separation from the membrane. The necessity to wait for two to three weeks before eggs can be effectively peeled brings with it the loss of freshness, flavor, shortened shelf life and the cost of storage.
Typically, the egg industry expects to process, i.e., peel around 80 thousand eggs per hour. Thus, the economic loss caused by improperly peeled eggs, by introduction of additional methods or by the necessary storage and refrigeration is extreme. When the quarter million eggs per day needs to be stored for two to three weeks in the refrigerator and otherwise additionally handled (loading the refrigerator and removal of eggs after aging) lots of room, energy and manpower is necessary for such aging process. Coupled with the loss of freshness, flavor and decreased shelf life after the peeling due to the prior two to three weeks storage needed for aging, the economical loss and cost is enormous.
And even when such storage time is reduced by methods for accelerated aging as shown in '828, the eggs submitted to noxious fumes still need to be peeled mechanically, facing all the problems described above. Also, their flavor is effected by ammonia or lime soda, and their appearance is that of the aged eggs.
Thus, it would be advantageous to have available a method for peeling hard boiled eggs which would allow fast, safe, economical and efficient peeling of the hard boiled eggs which would at the same time preserve the flavor, freshness, extend the shelf-life and eliminate an unnecessary cost of storage connected with aging or eliminate the noxious fumes treatment prior to boiling eggs.
This invention addresses all the above stated problems and offers a feasible solution to these problems by introducing chemical or chemical/mechanical egg peeling.